On 06/25/2014 04:37 PM, Andrew Bresticker wrote: > On Wed, Jun 25, 2014 at 2:42 PM, Stephen Warren <swarren@xxxxxxxxxxxxx> wrote: >> On 06/18/2014 12:16 AM, Andrew Bresticker wrote: >>> Add device-tree bindings for the Tegra XUSB mailbox which will be used >>> for communication between the Tegra XHCI controller and the host. >> >> Sorry for the slow review. >> >>> diff --git a/Documentation/devicetree/bindings/mailbox/nvidia,tegra124-xusb-mbox.txt b/Documentation/devicetree/bindings/mailbox/nvidia,tegra124-xusb-mbox.txt >> >>> +NVIDIA Tegra XUSB mailbox >>> +========================= >>> + >>> +The Tegra XUSB mailbox is used by the Tegra XHCI controller's firmware to >>> +communicate with the host. >> >> Isn't the mailbox an internal implementation detail of the XUSB controller. >> >> In other words, I'd naively think that there isn't a standalone generic >> mailbox that can be used by anything, but we just happen to want to use >> for XUSB. Rather, there's an XUSB controller, and part of the interface >> to that controller is a mailbox. > > Yes, the mailbox isn't an actual piece of hardware but rather the > interface through which the XUSB host and AP communicate. > >> As such, I don't think we want a standalone mailbox node in DT. Rather, >> we should add the required reg and interrupt values into the XUSB DT node. >> >> The driver for that XUSB HW module can either: >> >> a) Register as both a mailbox driver and an EHCI driver. >> >> b) Spawn a child device to instantiate the mailbox driver. >> >> Perhaps (b) could be assisted by using the MFD framework? > > So in the RFC series I did something like (a) where the XUSB host > handled the mailbox interrupt with both the PHY and host could > registering notifiers to handle the messages. It was suggested by > Arnd though that I make a separate mailbox driver. Instead of having > a both a host and mailbox node, I could have a single XUSB host node > and have the mailbox driver bind to that - thoughts? Yes, that sounds like what I meant by (b) above. I don't think you can actually have 2 drivers bind to the same DT node though, so it'd have to work something like: * XUSB host node causes a platform device to be instantiated * XUSB host driver probe()s against that * XUSB host driver's probe() creates a platform device for the mailbox * XUSB mailbox driver probe()s against that. Or, perhaps go completely MFD, and have 2 child devices (XUSB host and XUSB mailbox) instantiated by the MFD parent, which is what is in the DT. -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
